The objective of this pilot study is to investigate the presence of epidermal growth factor (EGF) and EGF-like proteins in breast duct fluid obtained by nipple aspiration, and their potential as putative markers of breast cancer risk. Radioimmunoassay and radioreceptor assay techniques will be used to determine the presence, and concentration, of these growth factors in breast fluids obtained from healthy premenopausal and postmenopausal volunteers, premenopausal women at risk for familial breast cancer or with preexisting benign breast disease, and premenopausal and postmenopausal breast cancer patients. The laboratory data obtained will be examined for the influence of such factors as age, menstrual status, stage of menstrual cycle, parity, lactation history, and oral contraceptive use on EGF-related proteins in breast duct fluid. A positive outcome for this pilot study would indicate the merit of a full-scale epidemiological study of growth factors in breast fluid and breast cancer risk.